Slice it with the crotch laying as flat a possible on the mill bed. Toe up, trim crotch with a chainsaw enough for mill head to pass and flat saw till to get a good wide opening cut. Flip the log till the flat side is on the bed, don't toe. Flat saw again till to get a good wide opening cut and the heart is boxed. Flip log till one flat is square against the dogs, toe up small end and saw till that edge is square. Flip log again till bark face is up and flat is square with the dogs (don't toe) and flat saw till square and the heart is boxed. Remember sap wood in Walnut is not a defect, roll log over once and saw lumber to desired thickness don't flip the cant (book matching), continue to saw down to mill bed.
When you get down near the pith you'll notice crotch figure in a few of the boards, number depends on how thick you cut your lumber and the diameter of the log. Length of figure below the crotch is dependent upon how old the tree is, the older the longer the figure. If your log is not atleast 12" in diameter, you might consider making it into fire wood, cause you be lucky to get a 6x6 crotch cant out of it and that's a lot of work for a 6x6.
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